Mountain snow packs and surface water are two main sources for agricultural water needs. Despite the possibility that farmland for crops like cotton, cantaloupes, broccoli, and garlic may be fallow in drought years, empty fields are not an option for crops like silage corn, which are main herd nutrition for dairies.
General strategies for coping with limited water include deficit irrigation of crops, improved irrigation efficiency and/or uniformity, improved crop genetics to develop varieties more tolerant to water stress, and change of crop species. For example, some dairy producers may forego planting silage corn, but instead choose to produce sorghum, which requires only two to three irrigations compared to corn's five to eight. The downside, however, is that use of sorghum could lead to reduced milk production.
An alternative strategy is the utilization of drip irrigation technology to produce dairy crops. For example, a few innovative dairy producers like DeJager farms have successfully produced silage corn with a drip irrigation system using synthetic fertilizers. A major constraint which deters the dairy industry's rapid transition to drip irrigation systems is that the use of synthetic fertilizers displaces dairy manure, the main source of nutrients for forage.
In addition to being a nutrient resource, dairy manure presents an important environmental challenge. Of particular concern is nitrogen pollution resulting from dairy manure applied via flood irrigation—one of the major sources of groundwater contamination in California. The problem is particularly acute in the San Joaquin Valley where the vast majority of the state's dairies reside, and where the long-term application of cow manure to crops has resulted in extensive groundwater degradation. San Joaquin Valley dairies are currently regulated under a general order issued in 2007 by the Central Valley Regional Water Quality Control Board which requires nutrients to be applied at agronomic rates. This presents a difficult challenge since existing flood irrigation methods were practiced over roughly 450,000.00 acres in 2015.
It is therefore desirable to have a technology that would enable the utilization of nutrients like liquid manure in drip irrigation systems with increased water use efficiency to address drought, and at the same time mitigate environmental challenges presented in managing the application of nutrients to fields. It is particularly desirable to have a technology that is able to maintain appropriate levels of nutrients obtained from wastewater blended with a second source of water on a continuous basis, automatically, without manual control or intervention.